A computing system is provided. A flash memory device includes at least one mapping block, at least one modification block and at least one cache block. A processor is configured to perform: receiving a write command with a write logical address and predetermined data, loading content of a cache page from the cache block corresponding to the modification block according to the write logical address to a random access memory device in response to that a page of the mapping block corresponding to the write logical address has been used, the processor, reading orderly the content of the cache page stored in the random access memory device to obtain location information of an empty page of the modification block, and writing the predetermined data to the empty page according to the location information. Each cache page includes data fields to store location information corresponding to the data has been written in the pages of the modification block in order.